Air compressor pump dying on me

[spills]

Sry admins if this is the wrong forum.

I'm in a bit of a pickle. About 2 years ago, I bought a 60 gallon air compressor from Northern Tool (here's a link to some specs I found online: Amazon.com: - Industrial Air Cast Iron Pump Compressor - 3.6 HP, 60 Gallon, Model# ILA7006056: Home Improvement. The tank says "Industrial Air", and Northern does not sell them anymore because they are discontinued. I use my compressor for powder coating and media blasting, so when it's in use it gets a good workout. About a week ago, I noticed that it kicked on and the belt was squeaking, and come to find out the pump had "locked" up. I say that because I shut it off, turned it back on, and it was working very hard to turn the pump. IT would finally turn the pump, and slowly begin to pick up speed. It now does this when the pump/motor is hot or cold, and it doesn't seem to happen all the time. I tore the pump apart to see if I could find any major problems; the valves seemed fine, and the only thing that I could find that looked a little suspect was that it seems like the cylinders and pistons are tapered. I couldn't find anyting wrong with it, so I put it back together and it still does the same thing.

So I have two questions for you.

1. Do you have any idea what would cause this? I've rebuilt car motors plenty of times, but I could not for the life of me figure this one out. Maybe it's something small that I'm missing, but I cannot find it.

2. I was looking at an Eaton Compressor 13 CFM Air Compressor Pump. I noticed that the bolt hole patterns are not the same (mine right now is about 6"x6" front-to-back and side-to-side). Would you just suggest drilling and remounting the pump on the mounting plate? And what kind of math would I need to do to figure out if my motor/pulley setup would work with that pump/pulley? My motor says it's rated at 3.7HP w/ 7HP max, 15A 220V.

I've found 1 or 2 people on eBay that are selling use pumps that would be a direct bolt in, but if I'm already spending the money I would really like to try and upgrade the pump as much as possible without upgrading the motor as well.

Forgive me if this is the wrong forum, I cannot find any info on the internet about any of this. Anyone got an idea?

[CarWiz]

Re: Air compressor pump dying on me

Sounds like a bad unloader valve. On most compressors, the unloader valve is part of the pressure switch. When the tank is up to pressure, the switch opens and depresses an unloader valve to release pressure on the head. It's the hiss you hear after the motor shuts off. It allows the motor to start the compressor without having pressure in the head/valves. When the pressure in the tank drops, the pressure switch turns on the motor and closes the valve.

It could be that all you need is a new pressure switch. Make sure you get the compressor type pressure switch with the unloader and not a well pump pressure switch. I think I've seen replacement switches at Northern.

[woodjames]

Re: Air compressor pump dying on me

Could be the check valve at the top of the tank, all compressors have this. When my unloader/bypass valve went it just leaked all the time, but I could see where it might lock up. Good news is that most of the time you can clean the check valve out with solvent. It'll be the brass fitting that goes between the tank and the flex copper pipe coming off the head. If it does happen to be the switch, you can find those anywhere, Just make sure that the amperage ratings match up the the FLA on your motor, or don't expect it to last too long(or run a motor starter). Actually I just check the specs you listed, 15 amps isn't too bad, you shouldn't have a problem finding one. As far as the switch goes, if a replacement only has one port, and yours has say 4, that's okay, you can tee off and get everything back on (pressure relief, etc...) The statement of it being intermittent suggests check valve, myself, I'd start there, it's a free fix. Just be sure you get the compression fittings on correct when you get things back together, 1/2 turn past finger tight I believe is the suggestion - but look it up to be safe. If you do replace the pump with a larger unit, do yourself a favor and get a two stage. You get what you pay for. Not sure on your motor, but 15amps seems a little low for that kind of cfm, but it would depend on if it is two stage or not. Pulleys can be determined by multiple websites out there, or the motor drive supply house you would normally get belts/pulleys from. Myself, I adjust the pressure down on the switch, and bump up the RPM a little at the head to get a little more CFM out of it, perfectly acceptible, just pick one or the other - Higher RPM and CFM with a loss in pressure / Higher pressure with a lower RPM and CFM - DON'T TRY TO DO BOTH!!!


-Jimmy

Sounds like a bad unloader valve. On most compressors, the unloader valve is part of the pressure switch. When the tank is up to pressure, the switch opens and depresses an unloader valve to release pressure on the head. It's the hiss you hear after the motor shuts off. It allows the motor to start the compressor without having pressure in the head/valves. When the pressure in the tank drops, the pressure switch turns on the motor and closes the valve.

It could be that all you need is a new pressure switch. Make sure you get the compressor type pressure switch with the unloader and not a well pump pressure switch. I think I've seen replacement switches at Northern.

[spills]

Re: Air compressor pump dying on me

Thanks for the quick responses guys. I checked the check valve on the top of the compressor first and all seemed well with it. I found a replacement switch at a local hardware store, it was slightly adjustable but not to my old switches specs. My old one cut in at 125psi and off at 150, this one's in at 100 and off at 140. I cycled it about 5-6 times with the tank at full pressure, everything seems to be fine now. I Was kinda stupid and just randomly adjusting screws (well, there's only 2 really). There was one in the center, plastic screw inside the housing, that I went too far with and when the compressor kicked off, it wouldn't release the pressure so it would drain back through and slowly leak out the breather on the pump for about 4 seconds, then it would finally release from the loader. I think I fixed that, all sesms to be good.

Now when you talk about bumping up the RPMs, how do you do that? I guess I really don't need 140+ psi, I don't think. My sand blaster uses something like 13cfm @ 90psi. I can't remember, it was a $30 siphon gun I bought at Home depot and I love it. But in bumping up the RPMs, would this make the tank run about the same amount of time as long as I reduce the pressure? I'm not sure how low I can go with this new switch I just bought.

[woodjames]

Re: Air compressor pump dying on me

Unless you are installing a new pump, it wouldn't be worth it. You can really only go about 10% reliably. With the price of a pulley to replace your old one(you'd only do the one on the motor). But then you would need a new belt, and a way to adjust the tension on the different length belt. It'd be a hassle, for a small difference-an extra 1.3scfm in your case. The two screws- one will set the cut out point, and the other adjusts the "span" between turn on and turn off. Glad to hear that things are up and running for you!

Thanks for the quick responses guys. I checked the check valve on the top of the compressor first and all seemed well with it. I found a replacement switch at a local hardware store, it was slightly adjustable but not to my old switches specs. My old one cut in at 125psi and off at 150, this one's in at 100 and off at 140. I cycled it about 5-6 times with the tank at full pressure, everything seems to be fine now. I Was kinda stupid and just randomly adjusting screws (well, there's only 2 really). There was one in the center, plastic screw inside the housing, that I went too far with and when the compressor kicked off, it wouldn't release the pressure so it would drain back through and slowly leak out the breather on the pump for about 4 seconds, then it would finally release from the loader. I think I fixed that, all sesms to be good.

Now when you talk about bumping up the RPMs, how do you do that? I guess I really don't need 140+ psi, I don't think. My sand blaster uses something like 13cfm @ 90psi. I can't remember, it was a $30 siphon gun I bought at Home depot and I love it. But in bumping up the RPMs, would this make the tank run about the same amount of time as long as I reduce the pressure? I'm not sure how low I can go with this new switch I just bought.